Hello Trailer,
I think you should try the works performance website at:
http://www.worksperformance.com/newproducts.html.
They have the ARS (adjustable)shocks for the grizzly 660. I did not look-up the Grizzly 600 but they should support this year also as they made a lot of Grizzlies that year.
All the best - Real Tree Griz 2002